The invention relates to intercalated clays and to methods of preparing such intercalated clays.
Layered naturally occurring and synthetic smectites, such as bentonite, montmorillonites and hecorites, may be visualized as a "sandwich" composed of two outer layers of silicon tetrahedra and an inner layer of alumina octahedra. These "sandwiches" or platelets are stacked one upon the other to yield a clay particle. Normally this arrangement yields a repeated structure about every nine and one-half angstroms.
Intercalated clays have been prepared by replacing the exchangeable cations with aluminum oligomers [U.S. Pat. No. 4,176,090; U.S. Pat. No. 4,248,739; U.S. Pat. No. 4,216,188; Lahav, N., Shani, U., and Shabtai, J.S., Clay and Clay Minerals, 1978, 26(2), 107; Lahav, N., and Shani, U., Clay and Clay Minerals, 1978, 26(2), 116; and Brindley, G. W., and Sempels, R. E., Clay Minerals, 1977, 12, 229] Zirconium oligomers [Yamanaka, S., and Brindly, G.W., Clay and Clay Minerals, 1979, 27(2), 119] and chromium oligomers (U.S. Pat. No. 4,452,901). The concept used is that aluminum cations hydrolyze and, through the addition of base to increase pH (see U.S. Pat. No. 4,176,070, Examples 16 and 21 and column 4, line 9), an oligomer of large molecular weight would form. Information on the deactivation and regeneration behavior of these catalysts is not well documented, however, it is generally recognized that they are not hydrothermally stable. (Imelik, B., et al., "Catalysis by Acids and Bases", Elsevier Science Publishers, Amsterdam, The Netherlands, 1985; and Occelli, M.L., Ind. Eng. Chem. Prod. Res. Dev., 1983, 22, 553).
It is known that 2:1 layered clays (e.g., bentonite, montmorillonite, and hectorite) can be intercalated to yield catalysts that exhibit activity and selectivity. The problem of insufficient thermal and hydrothermal stability of these clays is also well known (see Occelli, Marlo L., ibid., 533-559 and FIGS. 4 and 5). The pillars of these clays collapse at temperatures of over 650.degree. C. due to dehydroxylation and possible cation migration replacing aluminum.
Of the above-mentioned oligomers, aluminum oligomers have apparently been researched the most extensively. These oligomers can be formed in a variety of ways involving hydrolysis of the aluminum cation and are commercially available. During hydrolysis many cationic species are formed. Their equilibrium concentrations are very dependent upon temperature and pH. The maximum concentration of a desired species may be in a very narrow range of these variables. In addition, the species cannot be easily isolated or identified. If conditions are favorable, hydrolysis of the aluminum cation will proceed to form highly charged species [e.g., Al.sub.2 (OH).sub.2.sup.4+, Al.sub.3 (OH).sub.4.sup.5+ and Al.sub.13 O.sub.4 (OH).sub.24.sup.7+ ] (See Baes, C.F., Jr., and Mesmer, R.E., "The Hydrolysis of Cations", John Wiley and Sons, Inc., New York, N.Y., 1976.) Of particular interest is the cation Al.sub.13 O.sub.4 (OH).sub.24.sup.7+. From NMR studies, this species has been found to be the oligomer species responsible for the typical d.sub.001 spacing of 18 .ANG. in intercalate clays, (Plee, D., et al., J. Am. Chem. Soc. 1985, 107, 2362). The structure of this cation is a central four-coordinated aluminum atom surrounded by twelve AlO.sub.6 octahedra joined by common edges to form a Keggin-type structure. Because of its large charge and size it can easily replace exchangeable cations from the clay. Upon heating this oligomer forms a pillar of alumina yielding an intercalated clay with the characteristic d.sub.001 spacing with 18 .ANG.. At temperatures above 650.degree. C., dehydroxylation occurs and the pillars collapse (i.e., the intensity of d.sub.001 =18 .ANG. disappears).
Lahav, N., Shani, U., and Shabtai, J.S., ibid., p. 108, discloses that in the in situ formation method, the relevant metal cation is introduced into the clay exchange complex followed by in situ transformation into the hydroxide by raising the pH. In the crosslinking method, the metal hydroxide oligomer (polymorph) is prepared separately and then interacted with the clay particles, leading to the formation of a crosslinked framework. Application of the in situ method, which can be considered as a simulated natural process, leads to slow, gradual formation of the interlayered structure, whereas in the crosslinking method, the metal hydroxide oligomers crosslink the clay platelets in a fast reaction and the product is obtained almost instantaneously. If a freshly prepared metal hydroxide solution is used in the crosslinking method, both the in situ sequence and crosslinking probably take place, since the formation of stable oligomeric species is a slow process.
Occelli, M. L., et al., J. Cat. (1984), 90, 256-260, deals with the gas oil cracking selectivity is reported for a delaminated clay catalyst formed by the reaction of polyoxoaluminum cations with a synthetic small particle hectorite.
U.S. Pat. No. 4,510,257 (Lewis et al.) discloses a clay composition having silica pillars intercalated between the layers of an expandable, swelling layer, lattice clay mineral or synthetic analogue thereof. The silica pillars have at least two silicon atom layers. The clay composition is prepared by contacting a smectite type clay with a solution of a polyhedral oligosilsesquioxane of the following general formula (ZSiO.sub.1.5).sub.n (OSiZ.sub.2).sub.m, wherein n and m are zero or integers and n+m does not equal zero and Z is an organic moiety containing an atom(s) possessing cationic and/or coordinating characteristics with the proviso that all of the Z's on a particular oligosilsesquioxane need not be the same. A cracking catalyst is disclosed which is the silica intercalated clay product functionalized with ions which are hydrogen or the rare earth elements.
U.S. Pat. No. 4,176,090 (Vaughan et al. I) discloses pillared interlayered clay compositions which are prepared by reacting smectite-type clays with polymeric cationic hydroxo metal complexes of metals such as aluminum, zirconium and/or titanium. The interlayered clay compositions which possess substantial surface area in pores of less than 30 .ANG. in diameter are used as catalysts, catalytic supports and sorbents. The interlayered smectite can be prepared by reacting a smectite with a mixture of a polymeric cationic hydroxo inorganic metal complex, which is comprised of aluminum or zirconium complexes or mixtures thereof, plus water. The interlayered smectite is separated from the mixture. Column 6, lines 28 to 32, discloses that the intercalated clays are particularly useful in the preparation of catalysts which contain active/stabilizing metals such as platinum, palladium, cobalt, molybdenum, nickel, tungsten, rare earths and so forth.
U.S. Pat. No. 4,271,043 (Vaughan et al. II) is a continuation-in-part of U.S. Pat. No. 4,176,090 and also discloses the use of the copolymerization of ammonium and alkali metal hydroxides, carbonates, silicate and borate. Vaughan et al. II describes a process for preparing a pillared interlayered clay product having a high degree of ion exchange capacity. A smectite clay is reacted with a mixture of a polymeric cationic hydroxo metal complex, such as, polymeric cationic hydroxo aluminum and zirconium complexes, and water to obtain a pillared interlayered smectite. The interlayered smectite is calcined to obtain an interlayered clay product having greater than 50 percent of its surface area in pores less than 30 .ANG. in diameter. The calcined interlayered clay product is reacted with a base to increase the ion exchange capacity thereof. Some of the examples show the calcined interlayered clay being impregnated or exchanged using La(NO.sub.3).sub.3 or LaCl.sub.3.
U.S. Pat. No. 4,248,739 (Vaughan et al. III) is a continuation-in-part of U.S. Pat. No. 4,176,090. Vaughan et al. III discloses a method for preparing a pillared interlayered smectite clay product wherein a smectite clay is reacted with a mixture of polymeric cationic hydroxo metal complex and water to obtain a pillared, interlayered smectite having greater than 50 percent of its surface area in pores of less than 30 .ANG. in diameter after dehydration. The polymeric cationic hydroxo metal complex is a high molecular weight cationic hydroxo metal complex and copolymers thereof having a molecular weight of from about 2000 to 20,000. Example 3 hydrolyzes and polymerizes the aluminum chlorhydroxide by the addition of magnesium metal. Example 4 prepared a mixed Al-Mg polymer for pillaring interlayered smectite by dissolving AlCl.sub.3. 6H.sub.2 O and MgCl.sub.2.H.sub.2 O in deionized water and drying at 250.degree. F.
U.S. Pat. No. 4,452,910 (Hopkins) discloses a process for the preparation of stabilized, porous expanded layer, smectite clays. An aqueous slurry of smectite clay is contacted with an aged chromium-oligomer solution. A product clay is separated from the mixture. The product clay is dried, and is then stabilized by an inert gas atmosphere heat treatment, which includes a temperature above about 200.degree. C. to effect the production of a stabilized clay. The product is a porous catalytic material composed of a smectite clay having expanded molecular layers with a multiplicity of chromium-base "pillars" interposed between the molecular layers of the smectite clay.
U.S. Pat. No. 4,216,188 (Shabtai et al. I) discloses a process for the production of molecular sieves by reacting a colloidal solution of a monoionic montmorillonite having a concentration of 100 to 800 mg montmorillonite per liter, in the form of fully dispersed negatively charged unit layers at room temperature, with an aged sol of a metal hydroxide which has been aged for at least 5 days at ambient temperature. The metal hydroxide is aluminum hydroxide or chromium hydroxide. The reaction is conducted at a pH adjusted below the zero charge point having a residual net positive charge on the metal hydroxide, and under vigorous agitation, resulting in a rapid flocculation of the montmorillonite crosslinked with the metal hydroxide. The product is separated from the liquid phase and stabilized by heat treatment.
European Published patent application No. 130,055 (British Petroleum Co.) describes a stabilized pillared layered clay and a process for its production. This pillared layered clay consists of a layered clay pillared by the residue of a material which has reacted with the hydroxo groups of the clay structure. The process steps are reacting under substantially anhydrous conditions in an organic solvent, a layered clay having desired hydroxo groups associated therewith, and a material capable of reacting with the hydroxo groups to leave a residue of the material in the form of pillars for the clay.
European Published patent application No. 83,970 (British Petroleum Co.) discloses pillared clays prepared by reacting a smectite-type clay, such as bentonite, with an aqueous solution of a polymeric cationic hydroxo inorganic metal complex, such as chlorhydrol.
U.S. Pat. No. 4,238,364 (Shabati II) describes a cracking catalyst comprising a crosslinked smectite framework material functionalized with acid ions selected from the group consisting of the ions of hydrogen and rare earth elements. The preparatory method includes: preparing an acidic form of smectite clay including ions selected from the group consisting of hydrogen, cerium, gadolinium, lanthanum, neodymium, praseodymium, and samarium; crosslinking the acid form of smectite with oligomeric species of aluminum hydroxide; and stabilizing the crosslinked acidic form of smectite. Column 4, lines 15 to 23, of Shabtai II explains the difference between interlayer and lateral distance. As explained on line 54 of column 4, Shabtai II has obtained an interlayer spacing of 9 .ANG.. The lateral distance of 8 to 30 .ANG. mentioned in Shabtai II is the distance between the pillars as calculated by the ratio of reactant to clay (i.e., fully or partially reacted clay). In Claim 12 Shabtai II clarifys the matter of the 8 to 30 .ANG. as being the lateral distance in the interlayer space so as to provide a measure of the effective lateral (between the pillars, not between the layers of the clay) pore size. Referring to the drawings and col. 4, lines 15 to 23, the lateral distance (E) is termed the interpillar distance.
U.S. Pat. No. 4,579,832 (Shabtai et al.) describes a hydroprocessing catalyst possessing activity hydrocracking and/or hydrogenation activity. The catalyst includes a cross-linked smectite framework material prepared through interaction of the polyanionic smectite layers with oxygen containing oligomeric cations, that is, oligomeric hydroxo metal cations or oxo-metal cations. The catalyst also includes incorporated interlamellar components consisting of preselected combinations of catalytically active transition metal derivatives selected from the group consisting of Mo, Cr, Ni, Co, W and other transition metals. The transition metals are present in the form of metal derivatives selected from the group consisting of oxygen containing oligomers and oligomeric cations, and cations selected from the group consisting of mononuclear cations and binuclear cations. The catalysts can have lateral pore sizes of 11 to 35 .ANG.. Since Shabtai et al. used hydroxo aluminum oligomer, its intercalated clays had an interlayer distance of about 9 .ANG..
Shabtai, J., F. E. Massoth, M. Tokarz, G. M. Tsai and J. McCauley, 8th International Congress On Catalysts, (July 2-6, 1984), Proceedings, Vol. IV, pp. 735-745, discloses a series of cross-linked hydroxo-Al montmorillonite having basal spacings of 1.75 to 1.95 nm and surface areas of 300 to 500 m.sup.2 /g after heat treatment at temperatures of up to 873.degree.K. The series of pillared clay was in Ce.sup.3+ -, La.sup.3+ -, Li.sup.+ -and Na.sup.+ /Ca.sup.2+ -forms. The first three forms were formed by ion exchanging Na.sup.+ /Ca.sup.2+ -montmorillonite with aqueous solutions of CeCl.sub.3, LaCl.sub.3, LaCl.sub.3 and LiCl, respectively. The pillared clays had catalytic cracking activity. Details of some of the techniques and procedures were stated to be in McCauley, J., "Catalytic Cracking Properties Of Cross-Linked Montmorillonite (CLM) Molecular Sieves", MSc. Thesis, University of Utah, Salt Lake City, Utah (1983).
Tokarz, M. and J. Shabtai, Clays And Clay Minerals, Vol. 3, No. 2, (195), pp. 89-97, discloses partially hydroxo-Al montmorillonites prepared by the reaction of hydroxo-Al oligocations with Ce.sup.3+ - and La.sup.3+ -exchanged montmorillonites.
U.S. Pat. No. 3,962,135 (Alafandi) describes a method of producing thermally stable porous siliceous pellets having a high pore volume. The process steps are composed of acid leaching a sub-bentonite clay with H.sub.2 SO.sub.4, HNO.sub.3 or HCl to remove alumina and produce plastic clay, shaping it into a shaped particle and calcining the particle between temperatures of 900.degree. to 1300.degree. F. and repeating the above steps to produce particles containing about 80 percent of SiO.sub.2.
U.S. Pat. No. 4,436,832 (Jacobs et al.) relates to a bridged clay catalyst and a method of making it. The method consists of subjecting a mixture of an aqueous solution of at least one metal hydroxide and aqueous clay suspension to dialysis. (The hydroxide solution can be prepared before it is mixed with the clay suspension or by adding the hydroxide solution precursors to the clay suspension.) The clay catalyst is used for conversion of paraffinic or olefinic hydrocarbons. The hydroxides can be selected from the group formed by the hydroxides of the elements of groups IIB, IIIB, IVB, VB, VIB, VIIB, VIIIB, IA, IIA, IIIA, IVA, VA and VIA of the periodic table of the elements. Example 4 uses Ho(NO.sub.3).sub.3.6H.sub.2 O.
Pinnavia, T. J., "Intercalated Clay Catalysts", Science, Vol. 220, pp. 365-371, (1983) describes that intercalation of polynuclear hydroxo metal cations and metal cluster cations in smectites to produce pillared clay catalysts having large size pores. Page 366, while not dealing with pillaring, stated that the hydrated cations on the interlameller surfaces of the native minerals can be replaced with almost any desired cation by utilizing simple ion exchange methods and that homoionic exchange derivatives are readily achievable with simple hydrated cations, including hydrated transition metal ions. Pinnavia also stated that, although polynuclear hydroxo metal ions formed by hydrolysis in aqueous solution can yield pillared clays with interlayer free spacings, the number of metals that form suitable oligomeric species is limited. New approaches to the pillaring of smectite clays promise to extend the number of pillaring species. Page 371 states that an approach involving hydrolysis and oxidation of metal cluster cations, such as Nb.sub.6 C.sub.12.sup.2+ and Ta.sub.6 C.sub.12.sup.2+, affords clay pillared by small clusters of metal oxide approximately 10 .ANG. in diameter and stable to about 400.degree. C.
U.S. Pat. No. 4,367,163 (Pinnavaia et al.) discloses silica-intercalated clay. The material is prepared by exchanging at least a portion of the native metal ions of a swelling clay with complex silicon ions and then hydrolyzing the complex silicon ions. The intercalated material can be used as a catayst support for a rare earth.
U.S. Pat. No. 4,324,695 (Hinnenkamp) discloses transition metal carbonyl clusters intercalated with lamellar material, such as graphite or smectites, are prepared by reacting an intercalate of a transition metal halide with carbon monoxide at elevated temperature and at ambient to superatmospheric pressure. No rare earth element or compound is listed therein.
WO 8503016 (British Petroleum Co.) discloses silanized pillared interlayered clays and a method of producing it. The clay consists of a pillared interlayered clay chemically modified by incorporation therein of a silicon containing residue. The method comprises the steps of forming the precursor of a pillared interlayered clay, recovering the precursor of the pillared clay and optionally washing the recovered precursor, calcining the precursor obtained in the previous step to form the pillared interlayered clay and hydrolyzing a hydrolyzable silicon compound.
WO 8503015 (British Petroleum Co.) describes a silanized layered clay and a process of its manufacture. The clay consists of a layered clay chemically modified by incorporation therein of a silicon-containing residue in the absence of a polymeric cationic hydroxo inorganic metal complex. These clays are produced by hydrolyzing a hydrolyzable silicon compound, for example, a tetraalkoxysilane, in the presence of the layered clay and in the absence of a polymeric cationic hydroxo metal complex.
Japanese Kokai No. 58-55,332 shows a heat-resistant modified smectite clay catalyst with a large surface area, having a trinuclear ferric acetate cation. This clay catalyst is prepared by using bentonite modified montmorillonite in aqueous solution.
French Pat. No. 2,555,467 describes a thermally stable calcined clay mineral catalyst and a method of making it. The catalyst including 3.6 percent Fe.sub.2 O.sub.3, was prepared by calcination at 1000.degree. C. of a natural kaolinite and adding 0.8 percent of Ni by impregnation.
Pinnavia, T. J., "New Chromia Pillared Clay Catalysts", J. Am. Chem. Soc. (1985) 107, pp. 4783-4785 describes a method of making chromia pillared clays wherein solutions containing cationic polyoxychromium oligmers were prepared by the hydrolysis of chromium nitrate using Na.sub.2 CO.sub.3 as the base. To this solution was added typical smectite. Chromium was maintained in large excess during the pillaring reaction and after a reaction time of 1.5 hours, products were collected by centrifugation and washed free of excess salt.
U.S. Pat. No. 4,367,163 (Pinnavaia et al.) describes a clay composition having silica intercalated between the interlayers of clay and a method of preparing it. The main step in the preparation consists of exchanging at least a portion of the native metal ions of a swelling clay with complex ions and hydrolyzing the complex ions.
British Pat. No. 2,151,603 (British Petroleum Co.) describes a pillared layered clay having beryllium containing pillars that is produced by hydrolyzing a beryllium compound such as a salt and subjecting this treated compound to cation-exchanging with a cation-exchangable layered clay.
U.S. Pat. No. 4,469,813 (Gaaf et al.) discloses preparing pillared hydroisomerization catalysts by heating from 300.degree. to 450.degree. C. at subatmospheric pressure, a mixture of nickel synthetic mica montmorillonite with one or more polymerized hydroxy metal complexes, such as, a hydroxo aluminum polymeric solution.
U.S. Pat. No. 4,515,901 (Elatter) discloses a method of preparing an interlayered pillared clay by mixing a clay with a polar solvent, a soluble carbohydrate, and a soluble pillaring agent, drying the mixture, and then heating the mixture at a temperature between 100.degree. to 600.degree. C. to decompose the carbohydrate and form the interlayered pillared clay. (The temperature of stabilization is dependent upon the type of clay. The dehydroxylation temperature is different for each type of clay.)
U.S. Pat. No. 4,593,135 (Gregory) discloses a method for promoting the activity and/or extending the life of a cation-exchangeable layered clay catalyst in reactions susceptible to catalysis using protons.
Chemical Abstracts, 98:114423u (1983), discloses ion exchanging expandable clay minerals with large, cationic oxoaluminum polymers to introduce pillars between the clay layers. Between 540.degree. and 760.degree. C., the pillared clay collapsed during the catalytic cracking of a gas oil. (The collapse of the pillered clay is also time dependent.)
Chemical Abstracts, 104:189202x (1986), discloses preparing zeolite-like materials by treating suitable clays, for example, certain smectites, with aqueous solutions containing pure of mixed metal hydroxides, and then, after washing and drying, heating the resultant material at 100.degree. to 600.degree. C. The materials had cracking catalytic activity.
Chemical Abstracts, 104:50491x (1986), describes clays pillared with aluminum oxides or zirconium oxides.
Chemical Abstracts, 104:96367x (1986), states that Zr-pillared clays are more stable than equivalent Al-pillared clays. Chemical Abstracts, 104:88077e (1986), also deals with Zr-containing pillared interlayer clays. Chemical Abstracts, 104: 50491x (1986), states that, in the conversion of trimethylbenzenes, the selectivity of montmorillonites pillared by aluminum and zirconium oxides is not dependent upon interlayer distance. Chemical Abstracts, 102:45425h (1985), deals with pillaring smectite clay using polyoxo cations of aluminum.
U.S. Pat. No. 3,847,963 (Lalancette) discloses the production of graphite intercalated with a transition metal.
U.S. Pat. No. 3,842,121 (Ichikawa et al.) discloses forming a graphite-cobalt chloride interlayer complex, adding metallic potassium, etc., to form a three-component catalyst. A halide of a metal of groups VIB, VB, VIB, VIIB and VIII.
Kikuchi, Ehchi, et al., J. Cat., (1979), 57, 27-34, deals with lamellar compounds of graphite intercalated with ferric chloride.
In terms of catalyst usage and product value, catalytic cracking is the most important unit operation of the petroleum refining industry. In a typical fluid catalytic cracking unit, oil is contacted and vaporized by the hot fluidized catalyst in either the feed riser line or in the reactor. Cracking occurs in the riser at temperatures between 480.degree. and 520.degree. C. Catalyst and cracking products are mechanically separated, and occluded oil on the catalyst surface is removed by steam stripping at 500.degree. to 540.degree. C. Catalyst regeneration is completed by burning off coke deposits in controlled air at temperatures in the 600.degree. to 700.degree. C. range in the presence of small amounts of water. Then, from the regenerator, the catalyst flows into the incoming oil for reutilization. Catalyst stability at the thermal and hydrothermal conditions required for regeneration is essential for the maintenance of high activity and is critical in determining the commercial importance of a cracking catalyst.